THIS invention relates to a modular spring for a mattress foundation unit.
xe2x80x9cModular springxe2x80x9d is a term of art used to describe a spring which derive its resiliency from configurations other than coils.
A conventional mattress foundation unit, sometimes referred to as a xe2x80x9cbox springxe2x80x9d, generally includes a wooden base frame, modular springs and a mattress supporting wire grid that is supported above the wooden base frame by the modular springs. The modular springs are normally stapled to the wooden base frame below.
In some instances the top section of the modular spring is welded to the wire grid. One such configuration is disclosed in U.S. Pat. No. 5,967,499, wherein the top section includes two straight wire portions lying in angularly converging mirror image relation to each other. Another feature of the configuration is that four straight legs extend between the top section and the bottom section, with two of the legs extending in a first support plane from the top to the bottom section in angularly converging mirror image relation to one another, while one of the other two legs extends from the top section to the bottom section towards the first support plane. Often, the wire grid and spring modules are manufactured and pre-assembled by a first manufacturer before being transported to a second manufacturer. The second manufacturer will typically complete the final mattress foundation unit by connecting the pre-assembly to the wooden base frame and applying the padding and covering. The ease of assembly and stackability of the pre-assembly are important design criteria for the first manufacturer.
According to the invention there is provided a modular spring for a mattress foundation unit having a wire grid, a rigid base and a plurality of modular springs extending between the wire grid and the rigid base, each modular spring including:
a generally planar top portion connectable to the wire grid, the top portion including four partially curved, spaced apart members;
four legs extending downwardly from the top portion in an obtuse angular relation to the top portion and in diverging relation to each other, each leg interlinking two adjacent, partially curved members, and each leg terminating in a transverse foot portion, the foot portions being co-planar with one another and being connectable to the rigid base.
Typically, the top portions of the modular springs are welded to the wire grid.
In a preferred embodiment of the invention, each leg comprises two substantially straight spring members. Typically, the straight spring members are spaced apart and non-coplanar with one another.
Normally, the four partially curved members are spaced apart in a generally rectangular orientation.
Advantageously, the modular spring is symmetrical about planes that bisect opposing partially curved members.
Another aspect of the invention provides a stackable pro-assembly for a mattress foundation unit having a rigid base, the stackable pre-assembly including:
a generally planar wire grid including a plurality of grid wires arranged in a crisscross pattern;
a plurality of modular springs connected to the wire grid, each modular spring including:
a generally planar top portion connectable to the wire grid, the top portion including four partially curved, spaced apart members;
four legs extending downwardly from the top portion in an obtuse angular relation to the top portion and in diverging relation to each other, each leg interlinking two adjacent, partially curved members, and each leg terminating in a transverse foot portion, the foot portions being co-planar with one another and being connectable to the rigid base.